1. Field of the Invention
This invention relates generally to a refrigeration cycle apparatus, such as a refrigerator and an air-conditioner, incorporating a positive displacement type compressor as a cooling medium gas compressor, and more particularly to such a refrigeration cycle apparatus of the type in which part of a high-pressure liquid cooling medium in a refrigeration cycle is introduced into a compression chamber of the compressor so as to prevent the overheating of the compressor. Particularly, this refrigeration cycle apparatus can be suitably used over a wide operating pressure range, and its control is easy.
2. Description of the Prior Art
In various kinds of compressors, there has heretofore been used a method of preventing the overheating of the compressor by introducing part of a high-pressure liquid cooling medium, condensed by a condenser in a refrigeration cycle, into a compression chamber of the compressor. Also, in a refrigeration cycle apparatus (as disclosed in Japanese Patent Unexamined Publication No. 60-166778) employing a compressor of the set volume type, there has been used a method of preventing the overheating of the compressor by introducing a part of a high-pressure liquid cooling medium into a compression chamber of the compressor during its compression stroke via a connecting pipe communicated with the compression chamber.
To introduce the high-pressure liquid cooling medium, condensed by the condenser in the refrigeration cycle, into the compression chamber of the compressor during the compression stroke via the connecting pipe is only possible when the pressure within the compression chamber communicated with the connecting pipe is lower than the pressure of the high-pressure liquid cooling medium supplied to the connecting pipe. Therefore, the pressure within the compression chamber (which is communicated with the connecting pipe) during the compression stroke is determined by the position of connection of the connecting pipe relative to the compressor and the pressure at the low pressure side of the refrigeration cycle (i.e., the inlet pressure of the compressor) during the operation. Therefore, depending on operating pressure conditions, it is possible that the pressure within the compression chamber communicated with the connecting pipe becomes higher than the pressure of the high-pressure liquid cooling medium supplied to the connecting pipe, so that the introduction of the liquid cooling medium into the compression chamber is impossible, which may result in the overheating of the compressor. Also, depending on the operating pressure conditions, it is possible that the former pressure becomes very much lower than the latter pressure, so that an amount of introduction of the liquid cooling medium into the compression chamber become excessive due to this pressure differential, which may unduly increase the amount of electric power consumed by the compressor and may invite the overcooling of the compressor.
Thus, in the prior art, it has not been clearly described how to determine the position of connection of the high-pressure liquid cooling medium introduction connecting pipe relative to the compressor in order that the prevention of the overheating of the set volume-type compressor by the introduction of the high-pressure liquid cooling medium can be properly effected easily over a wide operating pressure range. Thus, with the prior art, it has been difficult to properly cool the compressor over a wide operating pressure range for the purpose of preventing the overheating of the compressor.